Zadania z chemii IB HL

Outline how each of the two by-products is removed from the benzoic acid during the recrystallization. By-product that is almost insoluble in hot water: ... By-product that is much more soluble than benzoic acid: ...

The volume of hot water used to dissolve the crude solid must be chosen carefully. Deduce the effect on the yield or on the purity of the recrystallized benzoic acid of using too much water and of using too little water. Too much water: ... Too little water:…

Describe the setup that would connect the $\ce{Sn^4+}/\ce{Sn^2+}$ half-cell to a second half-cell for comparing the two electrode potentials.

Most pools, including this lido, are dosed with sodium hypochlorite solution, $\ce{NaOCl(aq)}$, instead of chlorine gas. Suggest why pool operators avoid dosing the water with chlorine gas itself.

The student measures the hydrogensulfite concentration by titrating samples against a standard iodine solution, with starch as the indicator. Every three days, 25.00 $\mathrm{cm^3}$ of cordial is withdrawn from each flask, diluted to 250.0 $\mathrm{cm^3}$ with…

The student's results are plotted below. (i) Calculate the average rate at which the hydrogensulfite concentration in the 24 h flask decreased over the 12 days. Include units in your answer. (ii) Before starting, the student wrote this hypothesis: "The longer…

Sketch how the combined mass of the flask, the syringe and their contents would change with time during Experiment 1, and give a reason for the shape of your sketch. Label the axes 'Total mass' and 'Time'.

The enthalpy of combustion of $\ce{C15H32}$ is $-10\,040\ \mathrm{kJ\,mol^{-1}}$. (i) Calculate the maximum amount of energy that the complete combustion of 1.75 g of pentadecane can release. (ii) The energy from burning the 1.75 g sample is used to heat…